1. Field of the Invention
Known distribution panels or display panels include those called mosaic panels. On the panel surface of such mosaic panels, necessary display devices, measuring instruments, and the like are arranged on square paths of a grid formed into a lattice, crosswise in length and breadth, by using metal materials such as aluminum die cast or zinc aluminum die cast. Also known as display devices for these mosaic panels are illuminating display devices which implement illuminating display by means of a light source such as a light-emitting diode.
The present invention relates to illuminating display devices for use with a mosaic panel and, more particularly, to an illuminating display device which allows light-emitting diodes to be arranged at high densities and which can be mounted to or removed from the grid.
2. Description of the Prior Art
Conventional illuminating display devices have usually been provided in the following arrangement. As shown in FIG. 6, necessary display device is prepared as a through hole C in the surface of a blind tile B that can be mounted to or removed from a metallic grid A. Then an acrylic plate D having a light-pervious property is fitted into the through hole C. Further, an illuminating unit F which implements illumination with a relatively small number of light-emitting diodes E is fitted behind the tile B.
An illuminating unit is also known in which the portion corresponding to the tile B in FIG. 6 and the casing of the illuminating unit F are molded integrally together and an engaging piece is molded to the casing for engagement with the grid.
Still also known is a high-density illuminating display device, as shown in FIG. 7, in which a large number of light-emitting diodes E, E are arranged on a circuit board G at a high density as much as 16 dots in length and breadth each, for example. Conventional high-density illuminating display devices are, in general, arranged not to be mountable and removable to the grid of the mosaic panel, but to be fixedly arrayed by clamping with screws, each of the illuminating display devices being utilized primarily to display characters and others by combinations of light sources thrown into light emission.
The conventional illuminating display device in combination of the tile B and the illuminating unit F would result in a relatively low luminance because of a small number of light-emitting diodes. To make this illuminating display device higher in luminance and therefore easier to view, it may be arranged that the light-emitting diode itself is made higher in capacity or that, as indicated by two-dot chain lines in FIG. 7, a circuit board having the light-emitting diodes disposed thereon at a high density is accommodated in the tile.
However, if the circuit board G having the light-emitting diodes E arrayed thereon at a high density was accommodated in the tile B as shown in FIG. 7, heat generated by the light-emitting diodes E would accumulate dense within the tile B, adversely affecting the driving unit and others. Similarly, if high-capacity light-emitting diodes were accommodated in the illuminating unit F or in the integrated casing of the illuminating unit, heat would accumulate inside.
In particular, when illuminating display devices of high capacity having light-emitting diodes arrayed thereon at a high density are arrayed in a large number adjacent to the panel surface, as shown in FIG. 2, it has been established that the temperature of the illuminating display surface can reach approximately 80.degree. C. due to heat generated by the light-emitting diodes.